Electrolytic caustic-soda cell



N. STATHAM.

ELECTROLYTIC CAUSTIC SODA CELL. APPLICATION FILED MAY 31.1917. RENEWEDJUNE 30,1921.

UNITED sures PATENT- OFFICE}.-

NOEL STATHAM, 01'' HASTINGS 0N HUDSON, NEW YORK, ASSIGNOR TO INDUSTRIALI CHEMICAL COMPANY, OF NEW YORK, N. Y., A CQRPO'RATION OF NEW YORK.

ELECTROLYTIC CAUSTIG-SODA CELL.

Application filed May 31, 1917, Serial No. 171,835.

made a certain new and useful invention Relating to Electrolytic CausticSoda Cells, of which the following is a specification, taken inconnection with the accompanying. drawing, which form part of the same.

This invention relates especially to cathode diaphragm electrolyticcells particularly adapted for use in producing caustic alkali, such ascaustic soda, from salt, the cathode diaphragms being preferablyconstructed of special permeable material, so that the seepage ofelectrolyte therethrough occurs at such rate as to substantiallyovercome the back diffusion of the caustic soda through the smallpassages or interstices in the diaphragm. If desired also the diaphragmmay in some cases have its permeability regulated preferably by formingadjacent the discharge side of the diaphragm a relatively impermeablelayer of finer particles of asbestos or other material, which may beincorporated with the asbestos fibre or other material of which the bodyof the diaphragm may be formed.

In the accompanying drawing showing in a somewhat diagrammatic Wayillustrative embodiments of this invention,

Fig. 1 is a longitudinal section through a cell, parts being removed forgreater clea-rness.

Fig. 2 is a. transverse section thereof.

Fig. 3 is an enlarged horizontal section through one of the anodeelements; and

Figs. 4 and 5 are diagrammatic sectional views of the cathode diaphragmswhich may be used.

The cell body 1 may with advantage be formed of concrete and providedwith a suitable impervious lining 2 of vitreous tile, for instance. Theconcrete body may be strengthened and reenforced in suitable Ways,preferably by the use of stay rods or other strengthening devicesarranged outside the cell, these rods 31 being bolted or otherwiseconnected, for instance, to the stay connectors 44 at the corners of thecell body so as to hold the parts together and strengthen the constructon while minimizing all undesirable electrolytic action on the stay rodsand parts. As indicated in Figs. 1 and 2 suitable clamping plates, suchas Specification of Letters Patent.

Patented Apr. 4, 1922.

Renewed J'uner30, 1921. Serial No. 481,708.

42, may be cast or embedded in the cell body so as to support thecathode elements in connection therewith and these clamping plates maybe secured in position by suitable clamping bolts 11 which preferablypass through insulating protecting tubes 41 of hard rubber.

or the like to similarly protect these bolts against electrolyticaction. The cathode elements which may be clamped upon both 1 sides ofthe cell body to cover the open rectangular sides thereof as by theclamping dogs 32 may comprise the channel iron frames 45 in which theconcrete or other cathode backin 47 may be cast or otherwise formed,suitab e bearing bars, such as 23, being preferably cast into thisbacking so as to be substantially in line with the inner Y The cathodesin the edges of the frames. form of perforated plates 24 of steel orother suitable material may rest against these bearing bars and in turnsupport the cathode diaphragm 25 of suitable porous material, such assheets of asbestos paper, preferably allowing substantially uniformseepage at the different levels in contact with the electrolyte withinthe cell, although this is not necessary in all cases. As is usual inthe -'Hargreaves type of cell the cathode liquor entering the cathodechamber 33- by percolation or electrolytic action may run down into thecaustic drip space 46 from which it may be continuously drained by theusual drain pipes or passages not shown.

The anode elements within thecell may with advantage comprise the anodeposts l6 having bodies of raphite or other suit able material extendingup through anode apertures 4 at the top of the cell body, and preferablypermanently built into the cell body as by having the concrete or othercalking 43 around their upper portions while their lower portions may beembedded in the cell lining or otherwise cast into or permanentlysecured to the cell body. It is advantageous to protect these anodeposts against disintegration or other wasting influences in the cell andfor this purpose they may be first coated with a protecting insulatingcovering as shown in Fig. 3, in which the graphite anode post bodies 20are shown as enclosed in a: covering 16 of suitableinsulating material,wch, for instance, as hard rubber, which may be vulcanized in place onthe posts before they are assembled. The thickness of this rotectivecovering is of course. considerab y exaggerated 1n the drawing sincethis coating need only be an eighth of an inch thick or less to give thedesired permanence and elastic insulating properties. The anode platesare preferably removably mounted on these posts by suitable connectingdevices, such, for instance, as the double tapered connecting pins 19 ofgraphite or similar material which may fit tightl into a tapered hole inthe anode posts and a so into similarly taper-ed holes in the anodeplates 17, 18,which are thus mounted on each side ofthe post so as toproperly cooperate with the cathode diaphragins. it is, of course,understood that a suitable connector 15 may be cast upon or otherwiseelectrically connected to each anode post adjacent its top to conductthe current thereto and similar negative connections may be made withthe cathode frames or plates, as is Well known in this art.

As indicated in Fig. 1, the cell may with advantage be formed with adraw-off outlet, such as 6, arranged in the bottom of the cell body soas to be opened from time to time so as to completely withdraw the electrolyte from the cell, this outlet being, of course, normally closed bya suitable plug or other device. A brine inlet feed pipe 21 may becastinto the cell body so as to discharge brine through its inclinedlower end 22, a transverse connection, such as 34, bein preferablyprovided at about the liquid evel of the cell, which may be normallyclosed by a removable plug or covering allowing observation of the levelof the electrolyte from time to time. Another testing tube or opening 40may be arranged in the top of the cell body, this tube preferablyarranged adjacent one end of the cell, the

outlet pipe 10 preferably having a curved portion 7 in which a normallycovered cleanout hole 8 ma be arranged adjacent the bend so as to al owboth sections of'the pipe to be cleared by suitable devices, thereceiving end 14 of this chlorine discharge pipe preferabl communicatingwith the interior of the cel somewhat above the liquid level therein,which may be at about the-point indicated by the dotted line in Fig. 1.A brine drip discharge pipe, such as 12, may have a depending receivingend 13 within the cell and below the normal liquid level therein, thedischarge end of this pipe 12 outside the cell being preferably arrangedto drip into the trapped drip receiver 9 so that the amount of thisbrine drip which is discharged from the cell may be observed from timeto time as it passes into the trapped connection with the chlorinedischarge pipe and thus seals this connection iliane are used, so thatconsiderable percolation of brine can take place through the diaphragmseven when the current is not passing. For

this purpose the diaphragms may be formed.-

of asbestos board. or paper of a permeable character, the asbestos fibrebeing termed into heets of paper or cardboard of the do sired thickness,which of course provides numerous small diameter channels or capillarypassages through. the diaphragm through which the electrolyte tends toflow under the static pressure the anode chamber. If desired, the amountof percolation occurring throughout the different parts of the diaphragmmay be controlled by the use of more or less relatively impervious orfiner grained material incorporated in or applied to the diaphragmpreferably adjacent its discharge side. As shown in Fig. 4, the cathodediaphragm 26, the thickness of which is greatly exaggerated for the sakeof clearness, may have incorporated. therewith a layer 27 of lesspermeable material, this layer varying in thickness more or less betweenthe upper and lower parts of the diaphragm, so that at the bottom agreater thickness of this finer grain material is used whichcorrespondingly cuts down the seepage of electrolyte and in this way asubstantially uniform amount of seepage may take place throughout theentire diaphragm area. Another arrangement of diaphragm is shown in Fig.5 in which the thickness of the diaphragm is also greatly exaggerated.The diaphragm, mainly composed of substantially uniform sized particlesof asbestos fibre felted or laid together by paper makin methods mayhave a number of stepped or varying thickness portions of finer grainedor less ermeable material 29, 30 arranged prefera 1y adjacent itsdischarge side so that the seepage of electrolyte is thereby limited andrendered more or less uniform throughout the diaphragm area. For thesepurposes particles of much finer grained asbestos fibre may be used andthis material may be incorporated in any desired way with the fibrousmaterial forming the body of the diaphragm, which is preferably composedof substantially uniform sized fibrous particles, during itsmanufacture, or if desired a coating of this or other relativelyimpervious material may be applied to the partly or completely formeddiaphragm which is then preferably compacted so as to make asubstantially uniform thickness layer or sheet which cooperates to bestadvantage with the diaphragm mounting used. It is advantageous to havethese relatively impervious seepage regulat ing portions of thediaphragm at or adjacent its discharge side, since in this way solidparticles or impurities carried into the diaphragm by the electrolyte inwhich they are suspended are usually stopped and embedded in the moreporous open portions of the diaphragm where they exert comparativellittle influence in cutting down its permeabi ity. y

In the use of a cell of this character for the productionof caustic sodafrom ordinary salt brine the seepage of brine through the diaphragmpassages should preferably occur at such rate that undesirable diffusionof the caustic Soda formed adjacent the cathode cannot take place backthrough the diaphragm into the anode chamber. Caustic soda because ofits much greater solubility has a much greater tendency to becomedissolved in and diffused back through the electrolyte in the diaphragmthan sodium carbonate would, for instance, and to prevent thisundesirable action it seems necessary to have suflicient seepage orpercolation of the electrolyte through the diaphragm so that thevelocity at which the electrolyte passes through the small intersticesor capillary passages in the diaphragm is greater than the velocity ofback difiusion of the formed caustic soda electrolytically produced atthev surface of the cathode. The use of this cell has indicated thatgood results are secured when the cathode liquor seeping down throughthe cathode chamber 33 and into the drip space aG-at the bottom thereofcontains about as much salt in solution as it contains of caustic. Thecell is working at good efii- I ciency when there is about 110 grams perlitre of caustic soda in the cathode liquor to 100 to 110 grams ofdissolved salt therein. The salt'brine fed to the cell is preferably afairly concentrated solution of about 4:0

degrees Twaddell and it is supplied to the cell in such quantities as togive a slight brine discharge at the sight drip provided on the cellgiving a brine discharge of about th er square foot of diaphragmsurface, alt ough of course somewhat greater brine discharge may occurwithout undesirable results. Under these conditions the cell runsefiiciently without undesirable amounts of wasteful chloratedecomposition in the anode chamber and for weeks at a time cells of thischaracter have operated commercially with a current efficiency between90 and 94 per cent of the theoretical current required for producing thecaustic soda recovered. V

This invention has been described in connection with a number ofillustrative embodiments, forms, proportions, shapes, parts, materials,arrangements and methods of operation and use, to the details of whichdisclosure the invention is not of course to be limited, since what isclaimed as new and electrolysis of salt, an open sided .cell body formedof concrete and having an insulating vitreous lining, anodes mounted insaid cell body vided with a hard rubber insulating protecting coveringpermanently embedded in the lining of the cell body and projectingthrough anode apertures in the top of the same, renewable anode platescooperating with said posts and double tapered connector pins connectingsaid plates and posts, removable cathode frames secured to said cellbody to cover the open sides thereof, perforated cathode plates andpermeable cathode diaphragms in contact therewith clamped between saidcell body and said cathode frames, said diaphragms being of varyingpermeability at different heights to make the seepage of electrolytetherethrough and comprising anode posts procathode plates and permeablecathode diaphragms in contact therewith clamped between said cell bodyand said cathode frames.

3.- In electrolytic cells adapted for'the electrolysis of salt, an opensided cell body,

anodes mounted in said cell body and comprising anode posts providedwith an insulating protecting covering permanently embedded in-thebottom of the cell body and projecting through anode apertures in thetop of the same, renewable anode plates cooperating with said posts,removable cathode frames secured to said cell body to cover the opensides thereof, perforated cathode plates and permeable cathodediaphragms in contact therewith clampedbetween said cell body and saidcathode frames. 4. In electrolytic cells adapted for the electrolysis ofsalt, an open sided rectangular sectioned cell body formed of concrete,anodes mounted in said cell body, metallic strengthening memberscooperating with said cell body and arranged outside of the same,clamping plates embedded in the said cell body and secured thereto byremoving clamping bolts passing through said cell body and insulatedtherefrom by protecting tubes, removablecathode frames and clamping dogssecured to said clamping plates to clamp said cathode frames to saidcell body to cover the opensides thereof and having bearing barssubstantially flush with the inner faces of said frames, perforatedcathode plates and permeable cathode diaphragms in contacttherewithclamped between said cell body and said cathode frames, said diaphragnisallowing seepage of electrolyte therethrough at such rate as tosubstantially prevent back diffusion of the formed caustic soda throughsaid diaphragrns,

5. ln electrolytic cells adapted for the electrolysis of salt, an opensided rectangular sectioned cell body formed of concrete, anodes mountedin said cell body, metallic strengthening members cooperating with saidcell body arranged outside of the same, clamping plates embedded in thesaid cell body and secured thereto by clamping bolts passing throughsaid cell body and insulated therefrom, removable cathode frames andclamping dogs secured to said clamping plates to clamp said cathodeframes to said cell body to cover the open sides thereof, perforatedcathode plates and permeable cathode diaphragms in contact therewithclamped between said cell body and said cathode frames.

6. In electrolytic cells adapted for the electrolysis of salt comprisinga cell formed of concrete, anodes mounted. in said cell and comprisingcarbon anode posts provided with an elastic insulating protectingcovering permanently secured in the cell body and projecting throughanode apertures in the same, renewable graphitic carbon anode platescooperating with said posts and double tapered carbon connector pinsconnecting said plates and posts.

7. In electrolytic cells adapted for the electrolysis of salt,comprising a cell, anodes mounted in said cell and comprising carbonanode posts provided with an insulating protecting covering permanentlysecured in the cell body, renewable graphitic carbon anode platescooperating with said posts and tapered carbon connector pins connectingsaid plates and posts.

v 8. In electrolytic cells adapted for the electrolysis of salt,comprising a cell, anodes mounted in said cell and comprising carbonanode posts provided with a protecting coverlng, renewable carbon anodeplates cooperating with said postsand renewable Wedging carbonconnecting portions electricall connectin said posts and plates.

9. In e ectrolytic cells adapted for the electrolysis of salt,comprising a cell, anodes mounted in said cell and comprising carbonanode posts provided with at protecting covering and renewable carbonanode'plates cooperating with said posts and tapered carbon connectorpins connecting said plates and posts.

10. In electrolytic cells adapted for producing caustic soda by theelectrolysis of salt, a cell body, anodes mounted in said cell body,removable cathode frames secured to said cell body to cover the opensides there of, perforated cathode plates and permeable cathodediaphragms in contact therewith clamped between said cell body and saidcathode frames, said diaphragms being of substantially uniform thicknessand com-- prising a variable-thickness layer of relatively imperviousmaterial on their discharge sides to give said diaphragms varyingpermeability at different heights to make the seepage of electrolytetherethrough substantially uniform throughout different parts of thediaphragms, said ,diaphragms allowing seepage of electrolytetherethrough at such rate as to substantially prevent back diffusion ofthe formed caustic soda through said diaphragms.

11. In electrolytic cells adapted for pro ducing caustic soda by theelectrolysis of salt, a cell body, anodes mounted in said cell body,removable cathode frames secured to said cell body to cover the opensides there of, perforated cathode plates and permeable I cathodediaphragms in contact therewith clamped between said cell body and saidcathode frames, said diaphragms being of substantially uniform thicknessand com I prisin I a variable thickness layer to give said iaphragmsvarying permeability at different heights, said d-iaphragms allowinseepage of electrolyte therethrough at suc 100 rate as to substantiallyprevent back diffusion of the formed caustic soda through saiddiaphragms.

12. In electrolytic cells adapted for producing caustic soda by theelectrolysis Of 105 salt, permeable cathode diaphragms of substantiallyuniform thickness and comprising a variable thickness layer ofrelatively impervious material to give said diaphragms varyinpermeability at different heights, 110 said diaphragms allowing seepageof electrolyte therethrough at such rate as to substantially preventback diffusion of the. formed caustic soda through. said diaphragms.

13. In electrolytic cells, permeable cathode diaphragms comprising avariable thickness layer of relatively impervious material to give saiddiaphragms varying permeability at different heights. 7

14. In electrolytic cells, permeable cathode diaphragms comprising avariable thickness layer of relatively impervious material on theirdischarge sides to give said diaphragms varying permeability atdifferent 125 eights.

' NOEL STATHAM.

Witnesses: CHAS. H. DICKINSON, W. L. Comm.

